Isolation of fatty acids from aqueous solutions thereof



United States Patent.

3,017,434 ISOLATION OF FATTY ACIDS FROM AQUEOUS SOLUTIONS THEREOF JackJ. Bulloti, Dayton, Ohio, assignor to The Commonwealth EngineeringCompany of Ohio, Dayton, Ohio, a corporation of Ohio No Drawing.Original application Oct. 5, 1955, Ser. No. 538,764. Divided and thisapplication July 24, 1958, Ser. No. 754,508

2 Claims. (Cl. 260-526) This invention relates to improved methods forisolating fatty acids from aqueous or aqueous alkaline solutionsthereof, or for separating such acids in admixture with dicarboxylicacids, as a means for obtaining both types of acid in pure form. Thisapplication is a division of my application Ser. No. 538,764, nowabandoned.

There are any number of instances where it is desirable to isolate fattyacids from product process or synthesis solutions, or to separate thefatty acids from dicarboxylic acids also occuring in the solutions, theobject being to obtain both of the acid types in pure form.

For example, it is often desirable to isolate fatty acids 7 or solublesalts thereof from crude products containing them and resulting fromsuch large scale industrial processes as the saponification orhydrolysis of fats, oils, waxes or natural esters, or from oxidation ofproduct solutions in the x0 process.

It is also desirable to isolate fatty acids from crude productsresulting from the hot air oxidation of waxes, oils and gases either asfound naturally in petroleum or resulting from petroleum methods, aswell as from crude products produced by the oxidation or oxidativesplitting of unsaturated and cyclic hydrocarbons from coal, petroleumand various other large scale synthetic industrial chemical operations.

In general, it is desirable to have available a simple, reliable methodfor isolating individual or mixed fatty acids contained in aqueoussolutions obtained by procedures utilizing pure compounds or mixtures.

The compounds or mixtures comprising the fatty acids to be isolated maybe hydrolysis products of, for instance, nitrides, amides, esters, acylhalides, anhydrides, trihalides, diazoketones and hydantoins. Or theymay be oxidation products of primary alcohols, aldehydes, ketones,quinones, olefinic compounds, tertiary alcohols or certain acetylicderivatives, or the products resulting from ozonization or ozonolysis ofolefinic or acetylenic derivatives.

In addition to the mentioned methods resulting in aqueous solutionscontaining fatty acids to be isolated, there are special methods whichyield solutions of the fatty acids.

Such special methods include the oxidation of alkylsubstituted arylderivatives, of S-alkyl-Z-fu-oric acids, and of certain other cyclicalcohols, aldehydes and ketones, the oxidation and decarboxylation ofalpha-keto acids, the halogenation of methyl ketones, the dismutation ofaldehydes, carbonation of organo-metallic compounds, carboxylation ofaromatic nuclei, hydrolysis and decarboxylation of alpha-cyano acids,hydroxy acids, keto acids, aromatic acids and dioxolanes, the alkalifusion of unsaturated acids, hydrolysis and decarboxylation ofacylamino-malonic acids, and, also, the alkaline cleavage ofbeta-ketoalkylpyridinium iodides.

End products containing fatty acids to be isolated are obtained whennitn'les are subjected to alkaline hydrolysis.

-Nitriles may be subjected to alkaline hydrolysis using a strong basesuch as sodium hydroxide, potassium hydroxide, or a tetralkyl ammoniumhydroxide, or to acid hydrolysis using a mineral acid such as sulfuricor phosphoric acid. Among the available methods for prepar- 3,017,434Patented Jan. '16, 1962 ing these nitn'les insolution which may behydrolyzed to produce fatty acids may be mentioned:

(1) Action of alkali cyanides on organic halides (2) Action of alkalicyanides on sulfonate salts (3) Action of cuprous cyanide on diazoniumcompounds (4) Action of cyanogenating agents on phenols (5) Dehydrationof oximes (6) Alkylation of cyano-compounds (7) Decarboxylation of cyanoacids 8) Addition of hydrogen cyanide to unsaturated compounds (9) Cyanoamination of carbonyl compounds These are all standard methods resultingin solutions of nitriles which, on hydrolysis, yield straight chain orbranched soluble fatty acids having a carbon content 3 in the case ofstraight chain acids and 4 in the case of branched chain acids.

Hydrolysis of amides also yields fatty acids in solution which it may bedesired to isolate. Weaker acids such as acetic acid may be used toeffect the hydrolysis. A special instance is the use of nitrous acidwhere the reaction is driven to completion by evolution of nitrogen.Important method resulting in soluble fatty acids it may be desirable toisolate from solution include:

(1) Action of acylating agents such as acyl halides, carboxylic acids,and their anhydrides, esters and the like, on ammonia or primary,secondary or tertiary non-ring organic amines 2) Action of acidoly-ticagents on amides (3) Partial-hydrolysis of nitriles (4) Ketenation ofamines (5 Action of carbon suboxide on amines (6) Grignardization ofisocyanides 7) Rearrangement of oximes 8) Ammonolysis of diazoketones(9) Amination of lactones (10) Rearrangement of nitroparaffines Estersmay be hydrolyzed with relatively weak hydrolytic agents. In some caseshot water, aqueous alcoholic carbonates, or solutions or suspensions ofalkaline earth hydroxides are useful. While some of the methods involvethe use of a fatty acid in the preparation of the ester, they are notredundant since the synthesis may have been performed by-product-wisewithout intermediate isolation. Among the specific methods which may bementioned are the fol-lowing:

(1) Direct esterifications of acids with alcohols (2) Esterification ofalcohols with acyl halides or anhydrides (3) Ketenation of alcohols orphenols (4) Phosgenolysis of hydroxy derivatives (5) Ester exchange (6)Electrolysis of esters 7) Oxidation of aldehydes or ketones (8) Cleavageof keto-esters or lactones ('9) Reduction of keto-esters (10) Reductionof unsaturated esters Acyl halides may be hydrolyzed in a very simplemanner. In most cases, cold water effects the hydrolysis, and in othercases dilute weak acids or alkalis are satisfactory. The most commonpreparations of acyl halides utilize carboxylic acids, esters, or saltsand inorgnaic acid halides of the group V or Vi elements. Other methodsinclude:

(1) Halogenation of aldehydes (2) Acyl halide interchange with othercarboxylic acids in this method, the halide formed may be the desiredproduct and recovery of the released fatty acid may constitute animprovement in by-product separation.

Similar procedures apply to the hydrolysis and preparation ofanhydrides. One method that may be of economic significance is thereaction of cyclic olefinic anhydrides with dienes such ascyclopentadiene.

The hydrolysis of primary nitro-compounds obtained by direct nitrationof natural hydrocarbons or hydrocarbons derived from natural productsresults in solutions containing fatty acids which it may be desired toisolate. As an example, a standard hydrolytic procedure comprisesheating the nitro parafiins at l20140 C. for eight hours with 85%sulfuric acid. Important methods of preparing primary nitro-compoundsinclude:

(1) Vapor phase nitration of hydrocarbons (2) Reaction of primary alkylhalides with silver nitrate (3) Decarboxylation of nitro-acids (4)Reaction of alpha-bromo-acids and alkali nitrites (5). Action of nitrylchloride on unsaturated organic halides (6) Addition ofalpha-nitro-olefins to other nitro paraffins The oxidative proceduresmay be carried out in a variety of ways. Acid chromate solutions, acidand alkaline permanganate solutions, nitric acid, oxidant solution inacetic acid or anhydride may be used.

Primary alcohols may be prepared by a large number of methods of whichthe following are illustrative:

(1) Reduction of aldehydes (2) Reaction of carbonyl compounds with.metal alkoxides (3) Reduction of unsaturated or aromatic hydroxycompounds (4) Action of organo-metallic compounds on aldehydes or ofoxidant organo-metallic compounds on alkyl halides, or oforgano-metallic compounds on ketones, oxides, or epoxides, or esters (5The hydrolysis of esters or halides (6) The cleavage of ethers or oxides(7) The condensation of aldehydes, ketones, halogenated compounds, or ofcarbonyl compounds of other types (8) The oxidation of olefines,*acetylenes or other ethines 9) Hydrolysis of alpha-diazoketones (10)Reduction of esters Commonly used and commercially important methods ofpreparing aldehydes include:

(1). Action of formylating agents on aromatic hydrocarbons,cyano-compounds, phenols, and ketones (2) Cleavage of Schifi bases (3)Hydrolysis of gem-dihalides, alkoxydihydropyrans,

oximes, hydrazones, semicarbazones, aminebisulfite- 'aldehydes andacetals (4) Oxidation of aromatic side-chains (5) Oxidation of olefinsor methyl ketones (6) Reaction of primary alcohols with oxidants ofdehydrogenating agents (7) Reduction of olefinic aldehydes, acylhalides, thio,

or organic nitrites (8) Reaction of Grignard reagents with orthoformicesters of ethoxymethyleneaniline (9) Forrnylation of metal acetylides(10) Decarboxylation of glycidic or alpha-keto acids.

Ketones may be prepared by the following methods:

(1) Acylation of hydrocarbons (2) Oxidation of secondary alcohols, ordehydrogenation thereof (3) Ketone-alcohol oxidation-reduction exchange(4) Ozonolysis of olefine compounds (5) Oxidation of methylene compounds(6). Decarboxylation of acylmalonic acids (7) Grignardization oranalogous organo-metallic treatment of nitriles, anhydrides, acylhalides, amides, alpha, beta-olefinic ketones, esters and carboxylicsalts (8) Reduction of alpha, beta-olefinic ketones or of phenols (9)Cyclization of lactones (l0) Cleavage of substituted ring compoundsQuinones may be prepared by the oxidation of aromatic} hydrocarbons,phenols, aminophenols, aryldiamines, andhydroxynaphthoquinones. Quinonesmay be alkylated to other quinones. Ortho-aroylbenzoic acids may bequi-' nonized by use of ring closing agents. Finally, all of thesequinones may be converted to other quinones by use of the very samediene reagents such as the cyclopentadiene already referred to herein.

Olefinic compounds may be reacted directly with ozone, and then cleavedwith silver oxide to acids. Some of the product acids may be partlydecarboxylated yielding products containing fewer carbonyl groups. Somemethods for preparing olefins are the following:

(1) Dehydration of hydroxy compounds (2) Dehalogenation of dihalides ordehalogenation of monohalides (3) Dealkanol'ation of others or acetals(4) Pyrolysis of esters, methyl xanthates, amines, or organic aluminumbase salts (5) Reaction of olefinic acids with decarboxylating or v Allof the methods mentioned are, as will be understood by those skilled inthe art, methods which result in aqueous solutions of the soluble fattyacids.

Heretofore, there has not been available a convenient and economicalmethod for separating the soluble fatty acids (or alkylated fatty acid)from the solutions.

One object of the present invention is to provide a simple, relativelyinexpensive method for isolating the fatty acids or alkylated fattyacids from the dilute aqueous solutions and to separate them fromdicarboxylic acids that may be contained in the solution.

Another object of the invention is to provide a method for treatingaqueous solutions of mixed mono-carboxylic and. di-carboxylic acids toremove the former and leave the latter, substantially free from themonocarboxylic acid, in the solution.

These and other objects of the invention are achieved by converting thefatty acid to the corresponding insoluble aluminum soap whichprecipitates and may be separated from the solution by filtration, and,optionally, treating the aluminum soap with acid to liberate the freefatty acid therefrom.

The aluminum soap of the fatty acid is formed by mixing the aqueoussolution containing the fatty acid with an aqueous solution of awater-soluble aluminum salt.

The aqueous solution containing the fatty acid to be isolated may bealkaline or it may be saponified or made alkaline prior to mixingthereof with the aluminum salt solution. The solution of the fatty acidis not necessarily saponified or made alkaline before mixing with thealuminum salt solution.

Other conditions may be used. Thus, the aluminum salt solution can beadded to an acidic fatty acid solution and precipitation of the aluminumsoap effected by adding alkali to the mixture until the pH is increasedto 5.0 to 7.0. Or the aluminum salt solution can be added to asapouified fatty acid solution, rather than vice versa, which order ofaddition results in a mixture of the two aqueous solutions usuallyhaving a pH of 5.0 to 6.0.

The usual procedure is to add the saponified aqueous solution containingthe monocarboxylic acid or mixed monoand di-carboxylic acids to theaqueous solution of aluminum salt. However, as noted, this procedure maybe reversed. In any event, the pH of the aqueous medium consisting ofthe mixed solutions at which the insoluble aluminum soap precipitates isusually between 5.0-7.0.

The aluminum salts of the fatty acids HR are monohydroxy soaps of thetype AIOHR (where HR is C H O and R is C I-I O which are very insolublein water at pH 4 to 9.

The addition of mineral acid to the washed precipitate comprising thesoap of the monocarboxylic acid liberates the acid. Dicarboxylic acidswhich may be present in the aqueous solution along with themonocarboxylic acid form readily hydrolyzable salts which are notprecipitated with the aluminum soap of the monocarboxylic acid. Thus,when a solution comprising monoand di-carboxylic acids (or the alkylatedacids) is made alkaline and added to an excess (about 530% over thestoichiometric quantity) of an aqueous solution of an aluminum salt suchas aluminum sulfate, the aluminum soap of the monocarboxylic acid isprecipitated selectively and recovered from the solution, thedicarboxylic or alkylated dicarboxylic acid being contained in thesupernatant.

The procedure outlined is operable for the selective isolation of thesoluble monocarboxylic acid (or their alkylated derivatives) from thecrude products obtained by any of the processes described herein, aswell as from solutions of naturally occurring acids, acid distillates orany other aqueous source of the free organic acids.

One specific source of the monocarboxylic acid (or alkylated acid) isthe aqueous solution obtained by oxidizing cyclopentadiene or alkylderivatives thereof as described in my pending application Serial No.459,840, filed October 1, 1954, now abandoned.

Briefly, the method described in that application involves oxidizingcyclopentadiene or the alkyl derivative thereof in aqueous acid solutionor slurry by means of an appropriate oxidizing agent such as barium orpotassium permanganates, perrhenates, chromates, ferrates or periodates.Aqueous nitric acid may also be used.

The oxidation product is an aqueous solution of malonic acid oralkylated malonic acid. On heating the solution, the malonic acid isdecarboxylated to acetic acid, or in the case of alkyl malonic acid, tothe corresponding alkyl acetic acid.

The reactions involved may be illustrated as follows:

HC$I3H [O] HOOC\H/COOH A H H i) OH O H O O O H H C O 2 l C Hcyclopentadiene malonic acid acetic acid HC-OH HOOC H OOOH H II II l A HC C H C H 0-0 0 O H l C O 2 l R R H alkylalkylrnalonie acid alkylaceticacid cyclopentadiene HC$|)H [O] I-IOOC\1I11/C0OH A EH) OH I --O- R1?OOOH2 R2 R2 R1 E:

(1i alkyl malonic acid dialkyl dialkylcyclopentadiene acetic as: :l

While process (0) is operable, the introduction of a second alkyl groupinto monoalkyl sodium cyclopentadienyl by reacting the latter with analkyl halide does not give high yields.

It is found that branched chain acids are more easily obtained, thesebeing the products of decarboxylation of the oxidation product, dialkylmalonic acid in which the alkyl radicals are branched. Theoxidation ofthe dialkyl cyclopentadiene in which the alkyl radicals are branched,decarboxylation of the dialkyl malonic acid to the corresponding dialkylmonocarboxylic acid, and isolation of the latter from the solution asthe aluminum soap are illustrated in the following examples:

Example I Dicyclopentadiene containing an anti-oxidant was depolymerizedby boiling. The vapors were .led over a bed of powdered sodium hydride.Cyclopentadienyl sodium was formed in the bed, with evolution ofhydrogen. Efiiuent gases were led through a cold trap to removeunreacted cyclopentadiene as liquid which was saved for recycling. Aboutof the sodium hydride was converted to sodium cyclopentadienyl. t-Butylcholride was vaporized into the reaction chamber. Some isobutaneinitially evolved escaped from a trap provided for it. The trapcontained some liquid product; the reaction chamber was swept with apump while heated and the rest of the product was thus passed intothecold trap. To prevent contamination of the product with t-butylchloride, only 75 gms. (about 5 gms. less than the stoichiometricamount) thereof was vaporized originally. Some sodiumcyclopentadienyl.remained unreacted on the bed. The cut-off trap wasremoved and found to contain gms. of quite pure t-butylcyclopentadiene;(yield based on t-butylchloride, about 97%).

The t-butylcyclopentadiene was distilled into an excess of acidpermanganate solution, with stirring. When the oxidation was complete,excess permanganate Was reduced by passing sulfur dioxide gas into thesolution. The solution was then made alkaline by addition of a solutionof sodium hydroxide. Hydrogen sulfide was then passed in. A precipitateof sulfur and manganese sulfide formed. The solution was filtered. Thefiltrate contained alkali sulfates and disodium t-butylmalonate:

l\ H COONa Example II About 75 gms. of sec butyl chloride were passedover a bed containing about 88 gms. of sodium cyclopentadienyl. Theefiiuent vapors, which contained some butane, were led through 30%aqueous nitric acid. The nitric 7 acid solution was neutralized, andheated at 55 C. for one hour. It was cooled and passed into an excess ofalum solution. The aluminum soap precipitated was washed and added wetto 1:1 sulfuric acid. The supernatant layer, separated in 74% yield, was3-methylpentanoic acid.

Example Ill About 76 gms. of isobutyl chloride were passed over a bed of88 gms. of sodium cyclopentadienyl and the efiluent vapors, heated to350 F. were passed over a bed of a special catalyst. Oxidation to atransient malonic product which immediately decarboxylated occured. Thetrap contained a fluid which partially dissolved in water. The aluminumsoap which precipitated from the aqueous solution on addition to excessalum solution was recovered. On treatment with cold concentratedphosphoric acid, it yielded, as supernatant, 4-methylpentanoic acid:

in 30% yield.

(NoTE.-The special catalyst referred to was one designed to facilitatethe oxidation of dienes and was obtained by boiling ammonium molybdateand ammonium vanadate together in ammonia containing suspended silicauntil a sludge formed, the sludge was heated in a stream of air untilthe ammonium molybdovanadate formed decomposed to give a molecularlydispersed promoted catalyst on the silica body.)

In the alkylated dienes to be oxidized, the alkyl radical may containfrom 1-8 carbon atoms and, when more than one alkyl radical is present,the radicals may be the same or different.

The method of isolating the fatty acid described herein is by no meanslimited to the isolation of acids resulting from the decarboxylation ofmalonic acid. It is useful for the isolation of the normally solublemonocarboxylic acids contained in crude hydrolysis, oxidation or otherproducts as enumerated herein, and has, in fact, extremely wideapplication.

The solutions from which the fatty acids are recovered in the form ofthe aluminum soap may contain the fatty acid in concentrations fromatleast 5% up to 50% or more. The fatty acids may be mixed withdicarboxylic acid. The latter form readily hydrolyzable salts in theaqueous solution and are not precipitated with the aluminum soap of themonocarboxylic acid. In the case of aqueous solutions ocntaining mixedmonoand di-car boxylic acids only, the monocarboxylic acid may berecovered as the precipitated aluminum soap, the dicarscope of thedisclosure... Therefore, it is to be understood that it is not intendedto limit the invention to the specific details and procedures disclosedor to otherwise limit the invention except as defined in the appendedclaims.

What is claimed is:

1. The method of isolating water-soluble alkyl-substituted acetic acidfrom aqueous solutions containing the same and produced by hydrolysis ofbutylcyclopentaiene and in a solution mixed With other water-solublecarboxylic acids, which comprises saponifying the solution, adding thesaponified solution to an excess of an aqueous solution of awater-soluble aluminum salt selected from the group consisting of alumand aluminum sulfate to precipitate the insoluble aluminum soap of saidalky-l-substituted acetic acid, filtering the resultant acid soaps, andtreating the same with cold concentrated phosphoric acid.

2. The method of isolating 3,3-dimethylbutanoic acid from aqueoussolutions in which it is produced by hydrolysis oft-butylcyclopentadiene and wherein it is mixed with other Water-solublecarboxylic acids, which comprises saponifying the solution containingthe acid with aqueous sodium hydroxide, introducing hydrogen sulfideinto the resultant solution to precipitate sulfur and man ganesesulfide, filtering the solution to separate the precipitate and recovera filtrate containing alkali sulfates and disodium t-butylmalonate,acidifying the filtrate and heating to drive off carbon dioxide,saponifying the solution by the addition of sodium hydroxide and pouringthe same into an excess of aluminum sulfate solution to precipitate thealuminum soap of the resultant acid from the solution, filtering torecover the resultant precipitate and drying the same to provide apowdered mass, and admixing said mass with concentrated hydrochloricacid and then separating the resultant 3,3-dimethylbutanoic acidtherefrom.

References Cited in the file of this patent UNITED STATES PATENTS2,044,968 Bruson June 23, 1936 2,171,198 Urbain Apr. 29, 1939 2,356,340Murphree Aug. 22, 1944 2,447,064 Gebhart et a1. Aug. 17, 1948 2,501,806Akers Mar. 28, 1950

1. THE METHOD OF ISOLATING WATER-SOLUBLE ALKYL-SUBSTITUTED ACETIC ACIDFROM AQUEOUS SOLUTIONS CONTAINING THE SAME AND PRODUCED BY HYDROLSIS OFBUTYLCYCLOPENTADIENE AND IN A SOLUTION MIXED WITH OTHER WATER-SOLUBLECARBOXYLIC ACIDS, WHICH COMPRISES SAPONIFYING THE SOLUTION, ADDING THESAPONIFIED SOLUTION TO AN EXCESS OF AN AQUEOUS SOLUTION OF AWATER-SOLUBLE ALUMINUM SALT SELECTED FROM THE GROUP CONSISTING OF ALUMAND ALUMINUM SULFATE TO PRECIPITATE THE INSOLUBLE ALUMINUM SOAP OF SAIDALKYL-SUBSTITUTED ACETIC, FILTERING THE RESULTANT ACID SOAPS, ANDTREATING THE SAME WITH COLD CONCENTRATED PHOSPHORIC ACID.